Monday, September 8, 2014

universe - Did "big bang" radiate light?


According to present day physics nothing existed before the "big bang", even space and time. But often in documentaries, the "big bang" is shown as a ball of light that exploded at some point. If this were so, then photons should have been the first particles that flowed in the new universe. If we placed an imaginary observer at some visible distance from the "big bang" would they have been able to observe it?



Answer




You cannot place anything "outside" to observe the big bang because there was no space that thing could have existed in (as you rightly said in your first sentence). So any observer is necessarily right in the middle of the bang happening. The popular science illustrations showing a ball of light expanding are essentially wrong. There is nothing the ball expands into.


However, the early universe was very hot, and filled with radiation, but also very full of particles of all kinds due to the high energy density creating particles from the vacuum. It was opaque until matter was dilute enough to allow the passing of light, indicated below @380000yrs as the origin of the CMB. An observer right after the big bang wouldn't have seen anything (but that admittedly makes for poor images to show in TV ;) )(Image courtesy of Wikipedia)


Timeline of the universe


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